This invention relates generally to improvements in water purification systems of the type having a reverse osmosis unit or the like for removing dissolved ionic material and other contaminants from an ordinary supply of tap or feed water. More particularly, this invention relates to a relatively simple and reliable water quality or purity monitor for incorporation into a water purification system, wherein the monitor includes improved means for indicating the operational efficiency of the reverse osmosis unit.
Water purification systems in general are relatively well-known in the art of the type having a reverse osmosis unit for converting an incoming supply of ordinary tap or feed water into relatively purified water for use in cooking, drinking, etc. In general terms, the reverse osmosis unit includes a semi-permeable membrane through which a portion of the feed water supply is passed, such that the membrane acts essentially as a filter to remove dissolved metallic ions and the like as well as undesired particulate matter from the tap water. The produced supply of purified water is normally passed into a temporary storage reservoir or vessel where it is ready for dispensing and use, typically by operation of an appropriate faucet valve located adjacent a kitchen sink or the like. While the specific construction and operation of the purified water supply system may vary, such systems are exemplified by the systems shown and described in U.S. Pat. Nos. 4,585,554; 4,595,497; and 4,657,674.
In many instances, it is desirable to obtain an indication of the degree of purity of the purified water supply produced by the water supply system. Alternately stated, it is desirable to obtain an indication of the operating efficiency of the semi-permeable membrane within the reverse osmosis unit. In this regard, the level of water purity will depend upon and thus will vary in accordance with several factors, such as the cleanliness of the reverse osmosis unit membrane and the degree of contamination of the incoming feed water in a raw condition. The purity level of the produced purified water is normally indicated by a measurement of electrical conductivity, wherein a relatively high electrical conductivity correlates with a relatively low resistance and reflects a substantial quantity of remaining ionic material which has not been removed by the reverse osmosis unit. Conversely, a relatively low conductivity level indicates that a high proportion of ionic material as well as other contaminants have been removed. A failure of the purified water to meet certain purification criteria as represented by conductivity level indicates that the water supply system may not be operating properly, and particularly that the semi-permeable membrane within the reverse osmosis unit may need to be cleaned or changed.
In the prior art, test devices and systems have been proposed for use in measuring the conductivity level of produced purified water in a typical purification system. In some instances, the conductivity of the purified water is compared with the conductivity level of the incoming tap water in a raw condition, wherein such comparison indicates the operational efficiency of the reverse osmosis unit. In general terms, such test devices and systems have utilized one or more electrodes for contacting the purified water and, in some cases, for contacting the incoming feed water, to obtain the desired water conductivity readings. The electrodes are coupled to an appropriate operating circuit and source of electrical power to provide the desire purity level readings which can be indicated on a master scale or by illumination of appropriate indicator lights.
In the past, water quality monitor test devices have most commonly comprised self-contained portable units for use by service personnel in testing purified water, as described, for example, in U.S. Pat. No. 3,990,066. More recently, however, water purification systems have been equipped with compact monitoring devices integrated directly into the purification system, as shown, for example, in U.S. Pat. Nos. 4,623,451, 4,806,912, 3,838,774, and 4,708,791. While such integrated test devices beneficially permit frequent and regular test readings without requiring intervention by skilled service personnel, such devices must include an appropriate power source such as a battery power supply or means for connection to a standard household electrical power circuit. In battery powered systems, however, the power consumption requirements have generally not been optimized, such that the battery power source must be replaced with undesirable frequency. Alternatively, electrical connections to the household power supply may be undesirable and/or inconvenient with respect to the mounting location of other water purification system components.
There exists, therefore, a need for an improved water quality monitor test device designed for integration directly into a water purification system, particularly wherein the improved test device operates with extremely low power consumption requirements, such that a battery power source or the like can be used with an extended operating life, and in a manner consistent with extended service of electrodes. The present invention fulfills these needs and provides further related advantages.